Magnetic refrigeration and heating relies on the magnetisation and demagnetisation of magnetocaloric materials and the subsequent removal of the generated heat by a fluid flow. Active magnetic regenerator devices normally comprise a number of regenerator beds, each comprising magnetocaloric material. The regenerator beds are sequentially passed through a magnetic field generated by a magnet arrangement, e.g. comprising one or more permanent magnets. Thereby the magnetocaloric material of the regenerator beds is alternatingly magnetised and demagnetised, and heat is generated. A fluid flow is passed through each regenerator bed in order to remove the generated heat from the regenerator beds. The heat is subsequently removed from the device by means of a heat exchanger, through which the fluid passes.
The performance of such an active magnetic regenerator device is partly determined by the flow rate of the fluid passing through the regenerator beds, and also the exact timing of the fluid flow. Previous attempts to control the flow rate have relied on designing valves, which control the supply of fluid to the regenerator beds.
WO 03/050456 A1 discloses a rotating active magnetic regenerator comprising a valve system which ensures reciprocating fluid flow through the regenerator beds, in synchronization with the rotating movements of the magnet. This is obtained by means of individually rotating valves connected to the mechanism which moves the magnet.
EP 0 187 078 B1 discloses a rotating active magnetic regenerator comprising a valve system which ensures reciprocating fluid flow through the regenerator beds, in synchronization with the rotating movements of the magnet. The valve system comprises discs provided with orifices, the discs being arranged to rotate along with the magnet.
U.S. Pat. No. 8,037,692 B2 discloses a rotating active magnetic regenerator comprising a valve system which ensures reciprocating fluid flow through the regenerator beds. Synchronization between the rotating movements of the magnet and the fluid flow is obtained by carefully controlling one or more solenoid valves.
Common to the prior art documents described above is, that none of the active magnetic regenerator devices described therein provide an easy manner of ensuring that the flow profile matches variations in the magnetic field.